THE IMPORTED PIXE SAW FLY. 
LIFE HISTORY AND SEASONAL HISTORY. 
The experiments to obtain data on the life history and seasonal 
history of Diprion simile were distinct from those pertaining to the 
choice of host plant and also from those pertaining to the ability 
of the insect to reproduce parthenogenetically. Finns siflvestris 
was chosen as a host for this work because it seemed to be favored 
by the sawfly and because it had been shown to be a successful host 
in this locality by previous tests. In no instance was copulation 
observed, but opportunity for fertilization was provided by keeping 
constantly with each female at least two males in excellent condi- 
tion. These experiments were made with small cylinder cages of 
screen wire on a steel frame. 14 inches in diameter by 24 inches 
high, the top of which was removable to permit easy access to the 
interior for observation or handling the material. These cages were 
placed over young trees of Pinv.s sylvestris, and adults of Diprion 
simile were then libe- 
rated within. There 
were also certain spe- 
cial life-history and 
seasonal-history stud- 
ies, particularly some 
in which observations 
were made on larvne 
of this sawfly reared 
in isolation to deter- 
mine the number and 
duration of the -instars and the influence of the sex of the individual 
upon this phase of development. 
The data presented in the following account of Diprion simile 
show some sin^idar likenesses and contrasts with the life of the 
related Xeodiprion lecontei. s It would be well to emphasize that the 
imported pine sawfly has the same apparent division of the emergence 
period into Broods A and B. It differs somewhat from Leconte's 
sawfly in the course of its issuance, a fact which may be explained 
either as inherent in the species or as caused by change of environ- 
ment. The climate and other natural factors in the United States 
may be so different from those to which it is accustomed that it 
is unstabilized here. Should this prove true, the situation with 
regard to Diprion simile may become very different within a few 
years, and the insect may even become a more serious problem than 
it now promises to be. The imported pine sawfly has important 
life-history and seasonal-history advantages, and if it can become 
a recognized depredator while unstabilized by the conditions of this 
new environment, the destructive possibilities of the species when 
it is properly adjusted will be necessarily greater. In that case it 
may possibly present a new life history and seasonal history. 
—Diprion simile: Cocoons, a, Occupied by female, unopened; 
b, occupied by male, unopened: c, after emergence of female; d, 
male cocoon, showing emergence hole of a chalcid parasite; e, fe- 
male cocoon, showing emergence hole of a dipterous parasite. 
ADLXT EMERGENCE. 
The emergence of adults from the cocoons of a single colony of the 
larvae of Diprion simile occurs over a considerable period, approxi- 
mating a year. This emergence is not continuous, but divides itself 
• Middieton, William. 
10, p. 741-760. 1921. 
Leconte's sawfly, an enemy of young pines. In Jour. Agr. Research, v. 20, no. 
